1. Field of the Invention
This invention relates to a printer which cooperates with an electronic typewriter or a word processor, especially to a printer having a bi-directional printing function.
2. Prior Art
Various types of printers for printing character data stored in a memory means have been proposed. Many of them have a bi-directional shortcut printing function to minimize print head (carriage) movement and realize high-speed printing (for example, in U.S. Pat. No. 3,764,994). In order to minimize the distance for moving the carriage when it reaches the end of the printed line and is to be shifted to the next print line, the carriage is controlled to move from the current position, i.e., the end of the current print line, to the nearest end of the next print line. Namely, the carriage can move either in the normal direction (from left to right) along the order of the print data or in the reverse direction (from right to left), responsive to the end position of the next print line. As a result, the time required for moving the carriage to the next print line can be greatly reduced
The printer, however, is not necessarily used for exclusively printing the character data stored in the memory means. It is sometimes required to print the character data input by manual typing operation in real time. In a conventional printer with the bi-directional shortcut printing function, the last line is not necessarily printed in the normal direction. When the last line is printed in the reverse direction, the carriage finally stops at the left end of the last print line. Under such condition, if it is desired that following character data is input by manual typing operation, the carriage must be moved from the left end of the last print line to the currently required print position to subsequently print the character data input by manual typing. If the operator carelessly performs subsequent typing without moving the carriage to the last printed position, another character is printed over already printed character, which requires time and tedious correcting operations. Since this movement of the carriage is inharmonious with the input performance, it seems strange to the operator. Moreover, it is inconvenient that the carriage is moved from the left end position to the currently required print position every time manual input is executed and, as the movement of the carriage requires some time, prompt manual typing is prevented.